Conventional vehicular exterior mirror housings may be stamped from metal and painted for protection against the elements or molded from thermoplastic or thermosetting resins and painted black or to match the color of the vehicle body. In addition, certain prior known molded exterior rearview mirror housings include an in-molded black pigment but are otherwise unpainted and uncoated.
With reference to FIG. 8, the typical prior art decorative painting of a vehicular exterior rearview mirror housing A includes a series of layers including a primer layer B, a base or color coat layer C and a clear coat layer D. The paint compositions can be one or two component polyurethanes or acrylics in a typical assembly. Prior to painting, the molded resinous plastic housing is cleaned and dried. The cleaned housing surface is then sprayed with a primer B and allowed to cure. The primer layer improves adhesion of the subsequently applied color coat on the substrate housing A, and/or provides conductivity for electrostatic spraying of subsequent layers. The base or color coat C which contains pigment is applied over the primer B, the thickness depending on the hiding strength of the pigment therein. The base coat C is followed by a final clear coat D typically applied wet on wet over the base coat and again allowed to cure.
The above painting process is lengthy, time consuming, and adds significant expense to the manufacture of the mirror housing, regardless of whether the housing is metal or plastic. For example, extra materials are required, along with additional labor for painting and quality control, while process yields are typically less than 100% and result in additional losses. The painting process also requires a significant amount of capital equipment and dedicated factory floor space which itself adds further expense. Further, additional energy to accomplish the painting process is required along with emission control and waste recovery equipment which is closely monitored by government agencies to prevent the escape of volatile emissions from the paint. Compliance often requires significant additional capital for vapor recover systems.
On the other hand, unpainted, molded resinous exterior rearview mirror housings, when used in the harsh environment to which the typical vehicle is exposed, are susceptible to ultraviolet radiation degradation and weather affects such as crazing and cracking from the sun and temperature variations, scratching and abrasion in normal use, as well as attack from chemicals present in the atmosphere and vehicular fluids. This results in a housing whose appearance is reduced over time.
The present invention provides a coated exterior rearview mirror housing which overcomes the above problems of both painted, molded or metal exterior rearview mirror housings as well as unpainted, molded resinous mirror housings.